Implementing a "repeat command" function

Question

I'm working on a text editor, with much the same functionality as vi. I'm kinda stuck on the "repeat last command" feature. My thought was to get the most recent undoable edit, and then call a redo on it, but that doesn't seem to be working. Any ideas?

Answer 1

I'm implementing undo/redo as outlined in this page
http://java.sun.com/docs/books/tutorial/uiswing/components/generaltext.html
which basically consists of...
1) create a new instance of UndoManager (defined in javax.swing.undo)
2) register the document object of the text area as an UndoableEditListener
3) implement undo and redo actions that extend AbstractAction (I copied these from the above page)
4) call the UndoManager's undo and redo methods from the undo and redo actions.
My idea for repeat was to call the UndoManager's editToBeUndone() method (the most recent edit) and call the redo() method of the UndoableEdit object that it returns. However, the editToBeUndone() method is protected, so I created a class that extends UndoManager and overrode the editToBeUndone() method as follows.
public UndoableEdit editToBeUndone(){
     return super.editToBeRedone();
This could be wrong, but I'm pretty sure I've done something similar before.
The other thing that could be a problem is the redo() method of the UndoableEdit class. In the API, it reads "Re-apply the edit, assuming that it has been undone." I don't really know what it means by, "assuming that it has been undone." Is there somewhere I can find a more detailed description? It doesn't throw a CannotRedoException.
What is an undoable edit and not undoable are (presumably) defined in javax.swing.undo also.
Thanks for your reply,
jt